JPS5831258B2 - Durable coating material for mold casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold casting method, and more specifically, it uses composite aluminum phosphate as a binder, and metal oxides, phosphoric oxides, and silicate compounds are added to this. This relates to a durable coating material that can be mixed with metal nitrides and disulfides to provide a heat insulating effect and increase surface tension by mixing them with metal nitrides and disulfides.

As is well known, the role of the mold coating material in the mold casting method is to spray the mold coating material onto the mold to prevent welding between the mold and the molten aluminum.

Moreover, unlike mold release agents for die casting, with one application,
It is required to withstand several hundred castings.

Conventionally, this type of coating material has been made by mixing silica powder, calcium carbonate, iron oxide, mica, talc, graphite, clay, etc. with a binder such as water glass and bentonite, or by mixing aluminum phosphate. Graphite, talc, molybdenum disulfide, mica, etc. are used as binders and high-temperature lubricants.
A refractory powder containing alumina, silicic acid powder, zirconium silicate, titanium oxide, etc., which have heat insulating properties, was added to form a slurry and then applied.

The former, which was based on water glass, had poor adhesion to the mold, requiring fewer castings and poor workability.

Water glass already becomes glassy by the time the aluminum casting temperature reaches approximately 700°C, but since it contains a large amount of sodium ions, it absorbs moisture from the air, causing the coating to swell and need to be reapplied. was there.

In addition, the latter has the disadvantage that the binding force of the coating film itself decreases due to the dusting phenomenon of aluminum phosphate.

The adhesion of these coating agents to the mold is 5 to 10K.
g/i, cracks occur under harsh conditions, i.e., cracks occur due to a rapid temperature rise in the molten metal, or even when the button is turned off during the cooling process. For this reason, cracking is particularly easy on mold surfaces with large distributed frictional forces. This causes a welding phenomenon between the molten aluminum and the mold, making it difficult to release the product from the mold.

For this reason, the coating film must be repaired each time, and there is a limit to the number of times the mold can be cast, resulting in severe damage to the mold and shortening its life.

The purpose of the present invention is to solve the above-mentioned drawbacks, and to provide a durable coating that improves the adhesion with the mold and extends the number of castings, thereby improving work efficiency and meeting the needs of the foundry industry. He developed the mold material.

Previously, the Nikkan Kogyo Shimbun Publishing Co., Ltd. published “Ordinary Mold” No. 219~
221 pages (issue date: October 31, 1972) and Patent No. 902362 (Special Publication No. 30366 of 1972)
As is clearer, it is said that the coating material must have the following properties.

That is, (1) good applicability.

(2) The coating material must be well bonded to the mold so that the mold and the coating layer do not separate.

(3) No cracking or peeling of the coating layer occurs during drying.

(4) The coating layer should not crack or peel due to heating of the molten metal.

(5) Poor wetting with molten metal.

etc.

As a result of systematic research for the development of coating materials, we found that when aluminum phosphate is used as a binder, ions of other metals such as magnesium, zinc, iron, chromium, etc.
One or two or three types are dissolved and reacted to form a composite aluminum phosphate.

As aluminum phosphate, the atomic ratio of aluminum and phosphorus, that is, the ratio of kl/P, is 1 to 1.32/3. The ratio of 1<Al+
Me≦1°5.

In the range, the chair. The dissolution reaction method is as follows: (1) Add zinc carbonate or magnesium carbonate to aluminum phosphate while stirring to dissolve and react;
Synthesize composite aluminum phosphate.

(2) Synthesize composite aluminum phosphate by dissolving and reacting gelled iron hydroxide or chromium hydroxide in aluminum phosphate while stirring and slowly heating.

It has been found that the adhesion to the mold can be improved by using composite aluminum phosphate synthesized by the above method as a binder.

Adding other metal ions to aluminum phosphate
First, when the composite aluminum phosphate binder is dried to form a film, magnesium, zinc, iron, and chromium act as hardening agents, and after hardening, they do not absorb moisture from the air. Because it does not cause crystal changes due to moisture absorption, the so-called dusting phenomenon, it retains its initial adhesion over long periods of storage.

Therefore, once applied, the coating film can withstand long-term storage, continuous use, and intermittent use.

Second, when aluminum phosphate hardens, it becomes a polymer of aluminum trimetaphosphate and adheres closely to the mold surface, bonding with the metal surface of the mold in the form of Fe-0-P, which prevents P from participating in the reaction. -OH mixed powder and P-O-M
Because it has a three-dimensional structure while reacting as shown in e, it increases the adhesion between the mold and the coating film.

For these reasons, a coating film with good adhesion can be obtained without dry cracking, cracking due to thermal shock, or peeling.

To adjust heat insulation properties and surface roughness, use heat-resistant materials such as alumina, zirconium silicate, zirconium oxide, titanium oxide, zinc phosphate, iron phosphate, chromium phosphate, carborundum, and various clays. I can do it.

The composite aluminum phosphate film itself has a high surface tension with molten aluminum, but in addition, to worsen wettability,
By incorporating chromium oxide, graphite, boron nitride, molybdenum disulfide, silicon carbide, silicon nitride, talc, etc., it was possible to increase the surface tension at the solid-liquid interface with the molten metal.

Next, in order to explain the present invention in detail, the following examples will be shown.

Example 1 Composite aluminum phosphate (Al-Mg-PO4 system) 100 parts by weight alumina
150 Graphite 5
〃Chromium oxide 10 //water
100//Example 2 Composite aluminum phosphate (Al-Zn-PO4 system) 100 parts by weight alumina
150 Graphite
5 Chromium oxide 10 Water
100 Example 3 Composite aluminum phosphate (Al-Cr-PO4 system) 100 parts by weight Al
150 Graphite 5
〃Chromium oxide 10 〃Water
100//Example 4 Composite aluminum phosphate (Al-Fe-PO4 system) 100 parts by weight alumina
150 Graphite
5 Chromium oxide 10 Water
100 parts by weight Example 5 Composite aluminum phosphate (Al-Mg-Zn-PO,) 100 parts by weight Alumina 150 Graphite
5 Chromium oxide 10 Water
100//The above parts by weight are mixed in a ball mill for 30 to 120 minutes.

Add 0.2 to 0.3 parts water to 1 part of the slurry-like coating material mixed in this way, adjust it to make it easy to spray, and then apply it to the surface of the mold using a spray gun with a nozzle diameter of 1rIlIn. Apply and dry.

Further, at this time, the drying step can be omitted by heating the mold to 120° C. to 2000° C. and coating the surface of the mold.

All of these coating films are uniformly applied to a film thickness of 0.1 to 0.3 mm.

The sample thus prepared was placed in a furnace in an atmosphere of 700° C. for 30 minutes, and then allowed to cool.

After repeating this 10 times, the adhesion between the mold and the coating film was examined using a tensile tester.

As a result, the adhesion force was 30 kg/
The adhesion force was 3 times higher than the conventional value of 10 kg/i.

The product of the present invention was applied to an actual mold, aluminum was cast, and the number of consecutive castings was investigated, and it was found that over 1000 times could be cast.

Also, the surface of the aluminum casting was compared to the initial one.
I compared it with the previous one, and all of them were good quality products with uniform features.

The product of the present invention, which is characterized by using composite aluminum phosphate as a binder, is a one-component type and is stable over a long period of time.

Both have good coating properties and excellent adhesion to the mold.
It is a durable mold coating material that is extremely useful for casting, as it has appropriate surface tension, improves workability, and extends the life of the mold.

Claims (1)

[Claims] For aluminum phosphate in which the ratio of 1 atom to P atom, that is, the atomic ratio of Al/P is in the range of 1/3 to 1.32/3, the equation Al+Me/'P (Me: Zn,
Mg, Fe, Cr) molecules have a range of Al + Me of 1
An inorganic polymer of composite aluminum phosphate, which has been dissolved and reacted so that the value of <Al+Me≦1.5 is obtained, is used as a binder, and in order to give it a heat insulating effect, a metal oxide is blended, and further, A durable coating material for mold casting characterized by containing metal nitride in order to increase surface tension. 2. A durable coating material for mold casting according to claim 1, in which a metal phosphoric acid compound is blended with composite aluminum phosphate in order to provide a heat insulating effect. 3. A durable coating material for mold casting, which is made by blending a metal silicate compound with composite aluminum phosphate to provide a heat insulating effect in the coating material according to claim 1. 4. A durable mold casting material for mold casting, which is the same as the mold coating material described in Claim 1.2.3, in which a carbon compound is blended into composite aluminum phosphate in order to increase surface tension. 5. In the mold coating material according to any one of Claims 1.2.3, mold casting is made by blending metal disulfide with composite aluminum phosphate in order to increase surface tension. Durable coating material for use. 6. A durable coating material for mold casting, which is any one of chromium oxide, titanium oxide, and zirconium oxide, which is coated with a metal oxide as described in claim 1. 7 For the coating material described in claim 2, the metal phosphate compound may be zinc phosphate, iron phosphate, titanium phosphate,
A durable coating material for mold casting that is either chromium phosphate. 8. A durable mold casting material for mold casting according to claim 3, wherein the metal silicate compound is either zirconium silicate or talc. 9. A durable coating material for mold casting according to claim 4, wherein the carbon compound is graphite or silicon carbide. 10. A durable mold coating material for mold casting according to claim 4, wherein the metal disulfide is molybdenum disulfide. 11. A durable mold casting material for mold casting according to claim 1, wherein the metal nitride is boron nitride or silicon nitride.